errno: print stringified errors from errno

Fixes #52

Makefile: restructure cflags more

AFAIK should leave out `-march=native` to the callers. Also remove
`-gsplit-dwarf`, since that's very environment specific. inotify-info is
a small binary.

Add release automation

Once a tag is pushed to github, it will:

- create a "release archive"
- create the release with the release archive

The release will be a "pre-release draft", so a human will need to go
and make it "latest and greatest".

Example what happened in my fork when I pushed the tag:
https://github.com/motiejus/inotify-info/actions/runs/8833871736/job/24254232221
https://github.com/motiejus/inotify-info/releases/tag/untagged-821f6dd9487d26fa828c